<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>backdrop-filter css3背景都透明</title>
</head>
<style>
  *{
    padding: 0;
    margin: 0;
  }
  html,body{
    width: 100%;
    height: 100%;
    position: relative;
  }
  .dialog{
    width: 100%;
    height: 100%;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
  }
  .backdrop-box{
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    -webkit-backdrop-filter: blur(5px);
    filter: blur(5px);
    filter: opacity(25%);
    background-color: #B7CBE8;
    z-index: 1;
  }
  .dialog-box{
    position: absolute;
    width: 550px;
    height: 400px;
    background-color: #fff;
    text-align: center;
    z-index: 1;
  }
</style>
<body>
  <button id="open">打开弹窗</button>
  <div class="backdrop-box">
  </div>
  <div class="dialog">
    <div class="dialog-box">
      <div class="dialog-conter">
        欢迎打开弹窗
      </div>
      <div class="but-box">
        <button class="close-but">关闭</button>
      </div>
    </div>
  </div>
</body>
</html>
